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Beam IO for Google Cloud Pub/Sub Lite

There is a newer version: 0.23.0

/*
 * Copyright 2020 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.cloud.pubsublite.beam;

import static com.google.cloud.pubsublite.internal.ExtractStatus.toCanonical;

import com.google.api.gax.rpc.ApiException;
import com.google.cloud.pubsublite.Offset;
import com.google.cloud.pubsublite.Partition;
import com.google.cloud.pubsublite.SubscriptionPath;
import com.google.cloud.pubsublite.internal.CursorClient;
import java.util.Map;

class InitialOffsetReaderImpl implements InitialOffsetReader {
  private final CursorClient client;
  private final SubscriptionPath subscription;
  private final Partition partition;

  InitialOffsetReaderImpl(CursorClient client, SubscriptionPath subscription, Partition partition) {
    this.client = client;
    this.subscription = subscription;
    this.partition = partition;
  }

  @Override
  public Offset read() throws ApiException {
    try {
      Map results = client.listPartitionCursors(subscription).get();
      return results.getOrDefault(partition, Offset.of(0));
    } catch (Throwable t) {
      throw toCanonical(t).underlying;
    }
  }

  @Override
  public void close() {
    client.close();
  }
}